The field of art to which this invention pertains is citric esters.
Citric esters are well known compositions which have been used as plasticizers, lubricants and anti-settling additives for paints.
U.S. Pat. No. 2,122,716 describes long chain esters of citric acid, e.g., tridodecyl citrate, which have been used as plasticizers for resinous compositions.
U.S. Pat. No. 3,239,555 and 3,241,992 disclose bis-citric acid esters made by esterifying the acid groups with C.sub.1 to C.sub.18 alcohols and coupling the esters with dibasic acids. Such esters are useful as plasticizers for plastics.
In U.S. Pat. No. 3,251,792, the acid groups of citric acid are esterified with alkyl, aryl, cycloalkyl and haloaryl alcohols and the hydroxyl group is esterified with a carbonyl compound. Such compounds are used as stabilizers for polypropylene.
Lubricants for tinplate are disclosed in U.S. Pat. No. 4,287,741. Such lubricants are citric esters wherein at least one acid group is esterified with a one to 10 carbon alcohol and the hydroxyl group can be esterified with a 1 to 10 carbon acid.
Polyesters made by reacting glycols and allyl alcohol with citric acid are described in U.S. Pat. No. 2,936,297.
In German Pat. No. 1,228,736, distearyl citrate is disclosed as being useful to prevent settling of pigments in paints.
Internal processing lubricants for thermoplastics made from copolyesters of aliphatic diols, citric acid and long-chain monohydric alcohols are disclosed in British Pat. No. 1,450,273.